could i combine two 90's with a foot of pipe between them and street 90 for weir to create p trap? thought of this to get underneath conduit in underground .I wont do it , but am curious to hear all your inputs on why this is not an appropriate p trap. I know traps have to be between 2 and 4" deep but what about the length. Thanks all

i have seen old drum traps for bathtubs that had an inlet pipe longer than 1 foot. never seen a problem with them.
there is something in the code that says the p-trap must be self-scouring.

ALL plumbing must have a 'smooth integral bore'.


hj, PLEASE do not chime in with 'what about valves, etc'

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

That applies to drain lines. Threaded pipe and fittings do NOT have a "smooth bore" just by their design, unless they are Durham and then those are drain lines anyway.